Brain cancer radiotherapy:

Glioblastoma multiforme is the most
deadly of all brain tumors.
A primary brain tumor is a mass of
abnormal cells that start in the brain.
A metastatic brain tumor is brain
cancer that has spread from another
part of the body.


RADIOTHERAPY
Radiation therapy uses high energy
light beams (X-rays or gamma rays) or
charged particles (electron beams or
proton beams) to damage critical
biological molecules in tumor cells. If
enough damage is done to the
chromosomes of a cell, it will
spontaneously die or it will die the next
time it tries to divide into two cells.

Radiation therapy is usually done on
an outpatient basis with treatment
occurring each workday for a period of
several weeks. If the patient has had
surgery for the tumor, radiation
therapy typically begins a week or two
after surgery.

Radiation therapy is an effective
cancer therapy. In surgery, a surgeon
may be constrained in resecting the
cancer by the presence of critical
structures that cannot be removed.
The side effects of chemotherapy on
normal tissues far away from the brain
may limit the ability of a medical
oncologist to deliver appropriately
intensive treatment to a brain tumor. In
radiation therapy, a non-invasive
treatment can be given repetitively
over several weeks to months and can
be aimed specifically at the area where
treatment is needed, minimizing side
effects for uninvolved normal tissues.

This repetitive treatment is called
fractionation because a small fraction
of the total dose is given in each
treatment. The skills of the radiation
oncologist, physicist and dosimetrist
allow complex plans to be devised to
minimize side effects for normal
tissues. Radiotherapy can only be
performed with linear accelerator
technology.

The most noticeable long-term side
effect is a gradual decline in some
higher brain functions, which will occur
over a few years. Many patients notice
this as a memory problem. It would
seem reasonable that the area of the
brain irradiated and the dose of
radiation given would be important
factors that might influence this side
effect, but this has never been
conclusively proven. It is not certain
whether this gradual decline in higher
brain functions stabilizes after several
years, but many patients believe it
does.

Varian's Trilogy system  combines the
capabilities of other external beam
radiation technologies -- including
Cyberknife, Tomotherapy, and Novalis;